Since corrugated sheet cannot be bent transversely of its corrugations without great difficulty, it is endeavoured to avoid such constructions, by placing joints at angled locations, where the sheets are placed at an angle to one another, and then covering the joints with an angled strip bent from flat sheet. Alternatively, one sheet can be allowed to project over the joint location, when possible. Consequently, there is a need to be able to bend corrugated sheet easily, for instance so that corrugated sheet can be placed over an arris or roof ridge, thereby eliminating the need for separate ridge plates. When constructing sheds or similar, simple storage facilities, an advantage would be gained if one and the same corrugated sheet could be extended from the roof of a building down onto a side wall thereof.